Blood Purification Apparatus

ABSTRACT

A blood purification apparatus to which a blood circuit that allows a patient&#39;s blood to extracorporeally circulate and a blood purifier connected to the blood circuit and that purifies the blood in extracorporeal circulation are attachable, the blood purification apparatus including a dialysate introduction line through which dialysate is introduced into the blood purifier; a dialysate drain line through which waste dialysate resulting from blood purification performed by the blood purifier is drained from the blood purifier; and a concentration-detecting unit that detects a concentration of a predetermined substance in the waste dialysate resulting from the blood purification by the blood purifier and flowing through the dialysate drain line. The blood purification apparatus includes a control unit that establishes a state of equilibrium where the concentration of the predetermined substance in the waste dialysate flowing through the dialysate drain line and a concentration of the predetermined substance in the blood flowing through the blood circuit are equal or approximate to each other; a storage unit storing a value detected by the concentration-detecting unit in the state of equilibrium as an equilibrium value; and a clearance-calculating unit that calculates clearance in accordance with the value detected by the concentration-detecting unit and the equilibrium value stored in the storage unit, the clearance being a figure of merit representing a degree of solute removal by the blood purifier.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Application No.PCT/JP2018/038712, filed on Oct. 17, 2018, which claims priority toJapanese Application No. 2017-201429, filed on Oct. 17, 2017, the entiredisclosures of which are hereby incorporated by reference.

FIELD

The present invention relates to a blood purification apparatus capableof calculating clearance as a figure of merit representing the degree ofsolute removal by a blood purifier.

BACKGROUND

Hemodialysis treatment is a kind of blood treatment of purifying apatient's blood while causing the blood to extracorporeally circulate.In hemodialysis treatment, a dialyzer as a blood purifier through whichdialysate is allowed to flow is used, and a blood circuit through whichthe patient's blood is caused to extracorporeally circulate is connectedto the dialyzer. The blood and the dialysate are brought into contactwith each other through semipermeable membranes provided in thedialyzer, whereby waste matter in the blood or excessive water isremoved (the removal of excessive water is referred to as“ultrafiltration”). The blood purified by the dialyzer is returned tothe patient's body through a puncture needle. Meanwhile, the wastematter or the excessive water is drained to the outside together withthe dialysate through a dialysate drain line.

Appropriately evaluating and grasping the performance of the dialyzer isimportant in selecting a dialyzer suitable for each of individualpatients. One of indices that represent the performance of the dialyzeris clearance (CL), which is a figure of merit representing the degree ofsolute removal by the dialyzer. Clearance (CL) is an index of the volumeof urea (the volume of a predetermined substance) removed from the bloodhaving flowed into the dialyzer, and is represented by the unit of bloodflow rate (mL/min). Clearance is obtained by, for example, collectingthe patient's blood and testing the collected blood with an externalmeasurement device.

Such a method requires blood collection before blood measurement or thelike to be performed with an external measurement device. Therefore, forexample, blood purification apparatuses have been proposed by PTL 1 andPTL 2, in each of which an increase in Na⁺ in waste dialysate, resultingfrom the purification, at an increase in the concentration of Na⁺ in thedialysate on the supply side is regarded as a change in conductivity,whereby the clearance (Na⁺ clearance) is measured. Hence, the clearancecan be obtained without blood collection.

Examples may be found in PTL 1: U.S. Pat. No. 6,702,774 and PTL 2: U.S.Pat. No. 7,815,809, which are expressly incorporated by reference hereinfor all purposes.

SUMMARY

However, the above known blood purification apparatuses have a problemin that clearance cannot be obtained in real time (continuously) becauseNa+ needs to be supplied to the patient periodically.

The present invention has been conceived in view of the abovecircumstances and provides a blood purification apparatus capable ofobtaining clearance in real time.

According to the teachings herein, there is provided a bloodpurification apparatus to which a blood circuit that allows a patient'sblood to extracorporeally circulate and a blood purifier connected tothe blood circuit and that purifies the blood in extracorporealcirculation are attachable, the blood purification apparatus including adialysate introduction line through which dialysate is introduced intothe blood purifier; a dialysate drain line through which waste dialysateresulting from blood purification performed by the blood purifier isdrained from the blood purifier; and a concentration-detecting unit thatdetects a concentration of a predetermined substance in the wastedialysate resulting from the blood purification by the blood purifierand flowing through the dialysate drain line. The blood purificationapparatus includes a control unit that establishes a state ofequilibrium where the concentration of the predetermined substance inthe waste dialysate flowing through the dialysate drain line and aconcentration of the predetermined substance in the blood flowingthrough the blood circuit are equal or approximate to each other; astorage unit storing a value detected by the concentration-detectingunit in the state of equilibrium as an equilibrium value; and aclearance-calculating unit that calculates clearance in accordance withthe value detected by the concentration-detecting unit and theequilibrium value stored in the storage unit, the clearance being afigure of merit representing a degree of solute removal by the bloodpurifier.

According to the teachings herein, in the blood purification apparatustaught herein, the clearance-calculating unit calculates clearancethrough a mathematical expression CL=(Cd/Cdeq)×Qd (where CL denotesclearance, Cd denotes the concentration of the predetermined substancedetected by the concentration-detecting unit, Cdeq denotes theequilibrium value stored in the storage unit, and Qd denotes dialysateflow rate).

According to the teachings herein, in the blood purification apparatustaught herein, the control unit establishes the state of equilibrium byreducing or stopping the dialysate flow rate, increasing the blood flowrate, or causing the dialysate to circulate through the blood purifier.

According to the teachings herein, in the blood purification apparatustaught herein, the concentration-detecting unit includes alight-emitting portion that emits light toward the waste dialysate, alight-receiving portion that receives the light emitted from thelight-emitting portion and transmitted through the waste dialysate, anda detecting portion that detects absorbance in accordance with anintensity of the light received by the light-receiving portion, theconcentration-detecting unit detecting the concentration of thepredetermined substance in the waste dialysate in accordance with theabsorbance detected by the detecting portion.

According to the teachings herein, in the blood purification apparatustaught herein, the storage unit stores, as the equilibrium value, theabsorbance detected by the detecting portion in the state ofequilibrium, and the clearance-calculating unit calculates clearance inaccordance with the absorbance detected by the detecting portion and theequilibrium value stored in the storage unit.

According to the teachings herein, in the blood purification apparatustaught herein, the clearance-calculating unit calculates clearancethrough a mathematical expression CL=(Abs/Abseq)×Qd (where CL denotesclearance, Abs denotes the absorbance detected by the detecting portion,Abseq denotes the equilibrium value stored in the storage unit, and Qddenotes dialysate flow rate).

According to the teachings herein, the blood purification apparatustaught herein includes a time-lapse-change-calculating unit thatcalculates a time-lapse change in the concentration of the predeterminedsubstance in the blood flowing through the blood circuit, in accordancewith the clearance calculated by the clearance-calculating unit.

According to the teachings herein, the blood purification apparatustaught herein further includes a correcting unit that corrects theclearance calculated by the clearance-calculating unit, in accordancewith the time-lapse change in the concentration of the predeterminedsubstance that is calculated by the time-lapse-change-calculating unit.

According to the teachings herein, in the blood purification apparatustaught herein, dialysis dose Kt is obtained in accordance with theclearance calculated by the clearance-calculating unit, the dialysisdose Kt being an index not standardized by V denoting a total body-fluidvolume used in an index Kt/V representing a standardized dose ofdialysis performed by the blood purifier.

According to the teachings herein, in the blood purification apparatustaught herein, a tolerable number of times of reuse of the bloodpurifier is quantitatively evaluated in accordance with the clearancecalculated by the clearance-calculating unit.

According to the teachings herein, the blood circuit and the bloodpurifier are attached to the blood purification apparatus taught herein.

According to the teachings herein, a state of equilibrium is establishedwhere the concentration of the predetermined substance in the wastedialysate flowing through the dialysate drain line and the concentrationof the predetermined substance in the blood flowing through the bloodcircuit are equal or approximate to each other. Furthermore, the valuedetected by the concentration-detecting unit in the state of equilibriumis stored as an equilibrium value. Furthermore, clearance as a figure ofmerit representing the degree of solute removal by the blood purifier iscalculated in accordance with the value detected by theconcentration-detecting unit and the equilibrium value stored in thestorage unit. Therefore, clearance can be obtained in real time.

According to the teachings herein, the clearance-calculating unitcalculates clearance through the mathematical expression CL=(Cd/Cdeq)×Qd(where CL denotes clearance, Cd denotes the concentration of thepredetermined substance detected by the concentration-detecting unit,Cdeq denotes the equilibrium value stored in the storage unit, and Qddenotes dialysate flow rate). Therefore, clearance can be calculatedcorrectly and easily with the concentration-detecting unit, whichdetects the concentration of the predetermined substance in the wastedialysate.

According to the teachings herein, the control unit establishes thestate of equilibrium by reducing or stopping the dialysate flow rate,increasing the blood flow rate, or causing the dialysate to circulatethrough the blood purifier. Thus, a state of equilibrium can beestablished simply and easily.

According to the teachings herein, the concentration-detecting unitincludes the light-emitting portion that emits light toward the wastedialysate, the light-receiving portion that receives the light emittedfrom the light-emitting portion and transmitted through the wastedialysate, and the detecting portion that detects absorbance inaccordance with the intensity of the light received by thelight-receiving portion, the concentration-detecting unit detecting theconcentration of the predetermined substance in the waste dialysate inaccordance with the absorbance detected by the detecting portion.Therefore, the concentration of the predetermined substance in the wastedialysate can be detected accurately without bringing the wastedialysate into contact with any sensor or the like.

According to the teachings herein, the storage unit stores theabsorbance detected by the detecting portion in the state of equilibriumas an equilibrium value, and the clearance-calculating unit calculatesclearance in accordance with the absorbance detected by the detectingportion and the equilibrium value stored in the storage unit. Therefore,clearance can be obtained in real time by utilizing the ratio of theabsorbance that correlates with the ratio of the concentration of thepredetermined substance.

According to the teachings herein, the clearance-calculating unitcalculates clearance through the mathematical expressionCL=(Abs/Abseq)×Qd (where CL denotes clearance, Abs denotes theabsorbance detected by the detecting portion, Abseq denotes theequilibrium value stored in the storage unit, and Qd denotes dialysateflow rate). Therefore, clearance can be calculated correctly and easilyby utilizing the ratio of the absorbance that correlates with the ratioof the concentration of the predetermined substance.

According to the teachings herein, the blood purification apparatusincludes the time-lapse-change-calculating unit that calculates thetime-lapse change in the concentration of the predetermined substance inthe blood flowing through the blood circuit, in accordance with theclearance calculated by the clearance-calculating unit. Therefore, theconcentration of the predetermined substance in the blood flowingthrough the blood circuit at the current time or at any point of timethereafter can be estimated.

According to the teachings herein, the blood purification apparatusincludes the correcting unit that corrects the clearance calculated bythe clearance-calculating unit, in accordance with the time-lapse changein the concentration of the predetermined substance that is calculatedby the time-lapse-change-calculating unit. Therefore, even if theconcentration of the predetermined substance in the blood flowingthrough the blood circuit changes with the progress of the bloodpurification treatment, the clearance can be corrected correspondingly,with an estimation of the concentration to be observed after such achange.

According to the teachings herein, dialysis dose Kt as an index notstandardized by V denoting the total body-fluid volume used in the indexKt/V representing the standardized dose of dialysis performed by theblood purifier is calculated in accordance with the clearance calculatedby the clearance-calculating unit. Therefore, medical workers includingdoctors can grasp the index Kt, which is not standardized by V, incorrespondence with their intention.

According to the teachings herein, the tolerable number of times ofreuse of the blood purifier is quantitatively evaluated in accordancewith the clearance calculated by the clearance-calculating unit.Therefore, if the treatment is repeatedly given to one specific patientwith one specific blood purifier, the tolerable number of times of reuseof that specific blood purifier can be evaluated objectively andappropriately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a blood purification apparatus according to anembodiment of the present invention.

FIG. 2 is a diagram of a concentration-detecting unit included in theblood purification apparatus.

FIG. 3 is a flow chart illustrating a control process undergone by theblood purification apparatus.

FIG. 4 includes a graph illustrating, with an equilibrium value (Cdeq orAbseq), a relationship between dialysate flow rate (Qd) and a detectedvalue (Cd or Abs) observed in a process of establishing a state ofequilibrium by the blood purification apparatus (a process of reducingthe dialysate flow rate), and a graph illustrating a correspondingrelationship between dialysate flow rate (Qd) and clearance (CL).

FIG. 5 includes a graph illustrating, with an equilibrium value (Cbeq orAbseq), a relationship between blood flow rate (Qb) and a detected value(Cb or Abs) observed in a process of establishing a state of equilibriumby the blood purification apparatus (a process of increasing the bloodflow rate), and a graph illustrating a corresponding relationshipbetween blood flow rate (Qb) and clearance (CL).

FIG. 6 is a graph illustrating the value (Abs) detected by theconcentration-detecting unit (a solid line) and the equilibrium value(Abseq) (a broken line) that change with time.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described specificallywith reference to the drawings.

A blood purification apparatus according to an embodiment is providedfor purifying a patient's blood while causing the blood toextracorporeally circulate, and is applied to a hemodialysis apparatusintended for hemodialysis treatment. As illustrated in FIG. 1, thehemodialysis apparatus basically includes a blood circuit 1 for causingthe patient's blood to extracorporeally circulate, a dialyzer 2 as ablood purifier, a waste-liquid-concentration sensor 5 as aconcentration-detecting unit, and a dialysis device 6 capable ofperforming ultrafiltration while supplying dialysate to the dialyzer 2.The dialysis device 6 includes a dialysate introduction line 7 and adialysate drain line 8, a control unit 11, a storage unit 12, aclearance-calculating unit 13, a time-lapse-change-calculating unit 15,and a correcting unit 16.

As illustrated in the drawing, the blood circuit 1 basically includes anarterial blood circuit 1 a and a venous blood circuit 1 b each formed ofa flexible tube. The dialyzer 2 is connected between the arterial bloodcircuit 1 a and to the venous blood circuit 1 b. The arterial bloodcircuit 1 a is provided with an arterial (blood-removal orblood-collection) puncture needle a at a distal end thereof and with aperistaltic blood pump 3 and an air-trap chamber 4 a for bubble removalat respective halfway positions thereof. The venous blood circuit 1 b isprovided with a venous (blood-return) puncture needle b at a distal endthereof and with an air-trap chamber 4 b for bubble removal at a halfwayposition thereof.

When the blood pump 3 is activated with the arterial puncture needle (a)and the venous puncture needle (b) being punctured in the patient, thepatient's blood flows through the arterial blood circuit 1 a whileundergoing bubble removal in the air-trap chamber 4 a, and reaches thedialyzer 2, where the blood is purified and ultrafiltered. Then, theblood flows through the venous blood circuit 1 b while undergoing bubbleremoval in the air-trap chamber 4 b, and returns into the patient'sbody. Thus, the patient's blood is purified by the dialyzer 2 whilebeing caused to extracorporeally circulate through the blood circuit 1.In this specification, the side of the puncture needle provided forblood removal (blood collection) is referred to as the “arterial” side,and the side of the puncture needle provided for blood return isreferred to as the “venous” side. The “arterial” side and the “venous”side are not defined in accordance with which of the artery and the veinis to be the object of puncture.

The dialyzer 2 (the blood purifier) has, in a housing thereof, a bloodintroduction port 2 a, a blood delivery port 2 b, a dialysateintroduction port 2 c, and a dialysate delivery port 2 d. The bloodintroduction port 2 a is connected to a proximal end of the arterialblood circuit 1 a. The blood delivery port 2 b is connected to aproximal end of the venous blood circuit 1 b. The dialysate introductionport 2 c and the dialysate delivery port 2 d are connected to distalends of the dialysate introduction line 7 and the dialysate drain line8, respectively, extending from the dialysis device 6.

The dialyzer 2 houses a plurality of hollow fibers. The inside of eachof the hollow fibers serves as a blood flow route. The space between theouter peripheral surface of each of the hollow fibers and the innerperipheral surface of the housing serves as a dialysate flow route. Thehollow fibers each have a number of very small holes (pores) extendingtherethrough from the outer peripheral surface to the inner peripheralsurface, thereby forming a hollow fiber membrane. Waste matter,excessive water, and the like contained in the blood are allowed topenetrate through the membranes into the dialysate.

The dialysis device 6 includes a duplex pump (P), a bypass line 9connected to the dialysate drain line 8 in such a manner as to bypass adrain-side pump chamber of the duplex pump (P), and an ultrafiltrationpump 10 connected to the bypass line 9. The duplex pump (P) is providedover the dialysate introduction line 7 and the dialysate drain line 8.The duplex pump (P) is provided for introducing the dialysate into thedialyzer 2 through the dialysate introduction line 7 and draining thedialysate in the dialyzer 2, together with the waste matter in theblood, through the dialysate drain line 8. The duplex pump (P) may bereplaced with another device (such as a device employing a so-calledbalancing chamber or the like).

One end of the dialysate introduction line 7 is connected to thedialyzer 2 (the dialysate introduction port 2 c), and the other end isconnected to a dialysate supply device (not illustrated) that prepares adialysate at a predetermined concentration. One end of the dialysatedrain line 8 is connected to the dialyzer 2 (the dialysate delivery port2 d), and the other end is connected to a drainage unit (notillustrated). Hence, the dialysate introduction line 7 allows thedialysate supplied from the dialysate supply device to be introducedinto the dialyzer 2, while the dialysate drain line 8 allows wastedialysate resulting from the blood purification performed by thedialyzer 2 to be drained from the dialyzer 2 to the drainage unit.

The ultrafiltration pump 10 is provided for removing water (excessivewater) from the patient's blood flowing through the dialyzer 2.Specifically, when the ultrafiltration pump 10 is activated, the volumeof liquid drained through the dialysate drain line 8 exceeds the volumeof dialysate introduced through the dialysate introduction line 7.Hence, water is removed from the blood by a volume corresponding to theexcess.

The waste-liquid-concentration sensor 5 (the concentration-detectingunit) is provided on the dialysate drain line 8 in the dialysis device 6and detects the concentration of a predetermined substance (for example,the concentration of a substance such as urea or uric acid contained inthe waste dialysate) contained in the liquid (in the present embodiment,the waste dialysate drained from the dialyzer 2 as the blood purifier)that flows with the blood purification performed by the dialyzer 2. Asillustrated in FIG. 2, the waste-liquid-concentration sensor 5 basicallyincludes a light-emitting portion 17, a light-receiving portion 18, anda detecting portion 19. The light-emitting portion 17 and thelight-receiving portion 18 are positioned across the dialysate drainline 8 from each other.

The light-emitting portion 17 is a light source such as an LED and emitslight (ultraviolet light (UV)) to the liquid (in the present embodiment,the waste dialysate drained from the dialyzer 2). The light transmittedthrough the liquid is receivable by the light-receiving portion 18. Thelight-receiving portion 18 according to the present embodiment is alight-receiving device capable of generating a voltage corresponding tothe intensity of the light received. The detecting portion 19 detectsthe concentration of the waste dialysate in accordance with the voltagecorresponding to the intensity of the received light. The detectingportion 19 detects the absorbance in accordance with the intensity ofthe light received by the light-receiving portion 18, and thus detectsthe concentration of the predetermined substance in the waste dialysate(the concentration of urea or the like) in accordance with theabsorbance.

Specifically, when light is emitted from the light-emitting portion 17while the waste dialysate is flowing through the dialysate drain line 8,the light is transmitted through the waste dialysate flowing through thedialysate drain line 8. The light is absorbed by an amount correspondingto the concentration of the waste dialysate, and is eventually receivedby the light-receiving portion 18. Then, a signal representing theintensity of the light received by the light-receiving portion 18 (i.e.,the voltage generated in correspondence with the intensity of thereceived light) is transmitted to the detecting portion 19, where theabsorbance is calculated in accordance with the light intensitymeasured. Thus, the concentration of the waste dialysate flowing throughthe dialysate drain line 8 is obtained.

The waste-liquid-concentration sensor 5 according to the presentembodiment is an optical sensor including the light-emitting portion 17that emits ultraviolet light (UV) at a wavelength of about 300 nm (280to 320 nm). Alternatively, the waste-liquid-concentration sensor 5 maybe an optical sensor that emits another kind of light such as infraredlight, or an enzyme sensor or the like instead of an optical sensor.While the waste-liquid-concentration sensor 5 according to the presentembodiment is provided at a position of the dialysate drain line 8 onthe upstream side with respect to the duplex pump P (on the sideconnected to the dialyzer 2), the waste-liquid-concentration sensor 5may be provided on the downstream side with respect to the duplex pump(P).

The control unit 11 is a microcomputer or the like provided in thedialysis device 6 and establishes a state of equilibrium where theconcentration of the predetermined substance (the concentration of thewaste matter such as urea) in the waste dialysate flowing through thedialysate drain line 8 and the concentration of the predeterminedsubstance (the concentration of the waste matter such as urea) in theblood flowing through the blood circuit 1 (at the inlet of the dialyzer2) are equal or approximate to each other. Specifically, as illustratedin FIG. 4, while the dialysate flow rate (Qd) is reduced gradually, theconcentration (Cd) or the absorbance (Abs) is detected at each of pointsA to D by the waste-liquid-concentration sensor 5, whereby a graphrepresenting a relationship between the dialysate flow rate (Qd) and theconcentration (Cd) or the absorbance (Abs) can be obtained. The statewhere the concentration of the predetermined substance in the wastedialysate flowing through the dialysate drain line 8 and theconcentration of the predetermined substance in the blood flowingthrough the blood circuit 1 are approximate to each other indicates thatthe ratio between the two concentrations falls within a range of 0.7 to1.3. The ratio between the two concentrations is preferably within arange of 0.8 to 1.2, more preferably within a range of 0.9 to 1.1.

In such a state, even if the dialysate flow rate (Qd) is reduced fromthe point D, the concentration (Cd) or the absorbance (Abs) remainsconstant (such a constant value is referred to as equilibrium value(equilibrium concentration Cdeq or equilibrium absorbance Abseq)).Therefore, it is understood that a “state of equilibrium” has beenestablished where the concentration of the predetermined substance (theconcentration of the waste matter such as urea) in the waste dialysateflowing through the dialysate drain line 8 and the concentration of thepredetermined substance (the concentration of the waste matter such asurea) in the blood flowing through the blood circuit 1 are equal orapproximate to each other.

The storage unit 12 is electrically connected to the control unit 11 andto the waste-liquid-concentration sensor 5 and is capable of storing, asan “equilibrium value”, the value detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)in the state of equilibrium (i.e., the concentration (Cdeq) of thepredetermined substance or the absorbance (Abseq) observed in the stateof equilibrium). That is, the control unit 11 establishes a state ofequilibrium, and the value detected by the waste-liquid-concentrationsensor 5 in the state of equilibrium is stored in the storage unit 12 asan equilibrium value (an equilibrium concentration (Cdeq) or anequilibrium absorbance (Abseq)).

The clearance-calculating unit 13 is capable of calculating “clearance(CL)” in accordance with the value detected by thewaste-liquid-concentration sensor 5 and the equilibrium value (theequilibrium concentration (Cdeq) or the equilibrium absorbance (Abseq))stored in the storage unit 12. Clearance (CL) is a figure of meritrepresenting the degree of solute removal by the dialyzer 2. Theclearance-calculating unit 13 according to the present embodimentobtains clearance (CL) as follows.

Clearance (CL) is a function defined by blood flow rate (Qb), dialysateflow rate (Qd), and overall mass transfer coefficient (KoA) alone. It isknown that when the dialysate flow rate (Qd) is small enough withrespect to the blood flow rate (Qb) and the overall mass transfercoefficient (K₀A), the dialysate flow rate (Qd) serves as therate-determining factor, which establishes CL=Qd, regardless of theblood flow rate (Qb) and the overall mass transfer coefficient (K₀A)(see the following, for example: Akihiro Yamashita, “Basics of BloodPurification: The Japanese Journal of Clinical Dialysis”, 1999, Vol. 15,No. 8, pp. 101-105, the teachings of which are expressly incorporated byreference herein).

Assuming that the amount of adsorption to the purification membranes inthe dialyzer 2 is 0, blood-concentration-based clearance (CLb) based onblood concentration and waste-liquid-concentration-based clearance (CLd)based on waste-dialysate concentration are the same (indicate the samecontext). In such a case, clearance CL (CLb and CLd) can be obtained asthe product of the ratio between the concentration (Cd) of thepredetermined substance (urea) in the waste dialysate and theconcentration (Cbi) of the predetermined substance (urea) at the inletof the dialyzer 2 in the blood circuit 1, and the dialysate flow rate(Qd) (i.e., CL=(Cd/Cbi)×Qd Expression (a)) (see the following, forexample: Michio Mineshima, “Performance and Evaluation of Dialyzer”,“Clinical Engineering”, 2011, Vol. 22, No. 5, pp. 407-411, the teachingsof which are expressly incorporated by reference herein).

When dialysate flow rate (Qd) is the rate-determining factor, clearance(CL) is equal to dialysate flow rate (Qd), as described above. Hence,Expression (b) given below can be obtained through Expression (a), andExpression (c) given below can be obtained through Expression (b). Notethat “Cdeq” denotes the concentration of the predetermined substance(urea) in the waste dialysate when the dialysate flow rate (Qd) isreduced enough to be the rate-determining factor.

CL/Qd=Cdeq/Cbi=1  Expression (b)

Cbi=Cdeq  Expression (c)

That is, when the dialysate flow rate (Qd) is reduced enough to be therate-determining factor, the concentration (Cdeq) of the predeterminedsubstance (urea) in the waste dialysate becomes equal or approximate tothe concentration (Cbi) of the predetermined substance (urea) at theinlet of the dialyzer 2 in the blood circuit 1 (Cdeq=Cbi), whichcorresponds to the “state of equilibrium” according to the presentinvention. Hence, substituting Expression (c) into Expression (a) yieldsExpression (d) below.

CL=(Cd/Cdeq)×Qd  Expression (d)

The clearance-calculating unit 13 according to the present embodimentcalculates clearance through a mathematical expression (Expression (d)above) CL=(Cd/Cdeq)×Qd (where CL denotes clearance, Cd denotes theconcentration of the predetermined substance detected by theconcentration-detecting unit, Cdeq denotes the equilibrium value storedin the storage unit, and Qd denotes dialysate flow rate).

Furthermore, it is known that there is a correlation between the ratio(Cd/Cdeq) of the concentration (Cd) of the predetermined substance andthe ratio (Abs/Abseq) of the absorbance (Abs) at thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)(see the following, for example: F. Uhlin, I. Fridolin, L. G. Lindberget al., “Estimation of Delivered Dialysis Dose by On-Line Monitoring ofthe Ultraviolet Absorbance in the Spent Dialysate”, American Journal ofKidney Diseases, 2003, Volume 41, Issue 5, pp. 1026-1036).

Therefore, clearance (CL) can be obtained through Expression (e) givenbelow, by replacing the ratio (Cd/Cdeq) of the concentration (Cd) of thepredetermined substance in Expression (d) above with the ratio(Abs/Abseq) of the absorbance (Abs).

CL=(Abs/Abseq)×Qd  Expression (e)

In such a case, the storage unit 12 can store the absorbance detected bythe detecting portion 19 (the concentration-detecting unit) in the stateof equilibrium as an equilibrium value (an equilibrium absorbanceAbseq), and the clearance-calculating unit 13 can calculate clearance inaccordance with the absorbance (Abs) detected by the detecting portion19 and the equilibrium value (Abseq) stored in the storage unit 12.

The clearance-calculating unit 13 in the above case calculates clearancethrough a mathematical expression (Expression (e) above)CL=(Abs/Abseq)×Qd (where CL denotes clearance, Abs denotes theabsorbance detected by the detecting portion, Abseq denotes theequilibrium value stored in the storage unit, and Qd denotes dialysateflow rate).

A display unit 14 is capable of displaying the clearance (CL) calculatedby the clearance-calculating unit 13 and is, for example, a displayscreen of the dialysis device 6, or a monitor or the like connected tothe dialysis device 6. Since the clearance (CL) calculated by theclearance-calculating unit 13 is displayed by the display unit 14,medical workers including doctors can grasp the clearance accurately.Therefore, the blood purification treatment (dialysis treatment) can beperformed smoothly.

When the blood purification treatment progresses and the concentration(Cb) of the predetermined substance in the blood flowing through theblood circuit 1 changes (i.e., when the concentration is reduced withtime), the absorbance (Abs) as the value detected by the detectingportion 19 of the waste-liquid-concentration sensor 5 changes(decreases) as illustrated by the solid line in FIG. 6 from Abt0 (attime t=t0) to Abt1 (at time t=t1), Abt2 (at time t=t2), and Abt3 (attime t=t3). Meanwhile, the equilibrium value (the equilibrium absorbanceAbs) also changes (decreases) as illustrated by the broken line in thedrawing from Abst0 to Abst1, Abst2, and Abst3. Such changes also applyto the concentration (Cd) of the predetermined substance detected by thewaste-liquid-concentration sensor 5.

Therefore, the establishment of a state of equilibrium by the controlunit 11 and the storing of an equilibrium value (an equilibriumconcentration Cdeq or an equilibrium absorbance Abseq) by the storageunit 12 are performed at predetermined intervals (for example, at eachof times t1, t2, t3, and t4) during the blood purification treatment,and clearance (CL) is calculated by the clearance-calculating unit 13and is changed each time. Thus, the accuracy of the calculated clearancecan be increased.

The time-lapse-change-calculating unit 15 calculates a time-lapse change(Cb(t)/Cb(0)) in the concentration (Cb) of the predetermined substancein the blood flowing through the blood circuit 1, in accordance with theclearance (CL) calculated by the clearance-calculating unit 13.Specifically, assuming a case of a solute to which a single-compartmentmodel is applicable, it is known that the time-lapse change in (Cb) iscalculable from (CL) and total body-fluid volume (V), as can be seenfrom Expression (f) given below (see the following, for example: MichioMineshima, “Basics of Performance Evaluation of Blood Purifier”, NihonMedical Center Ltd. (Tokyo), 2002, pp. 14-17 the teachings of which areexpressly incorporated by reference herein). Note that “t” denotes anarbitrary dialysis time in the blood purification treatment.

Cb(t)/Cb(0)=exp(−(CL×t)/V)  Expression (f)

Therefore, the concentration (Cb(t)), which is a value obtained at timet as the concentration (Cb(0)) of the predetermined substance in theblood flowing through the blood circuit 1, can be obtained throughExpression (f) above, in which the clearance (CL) calculated by theclearance-calculating unit 13, the patient's total body-fluid volume(V), and the time (t) are used as parameters. Hence, the concentrationof the predetermined substance in the blood flowing through the bloodcircuit 1 at the current time or at any point of time thereafter can beestimated.

The correcting unit 16 corrects the clearance (CL) calculated by theclearance-calculating unit 13, in accordance with the time-lapse change(Cb(t)/Cb(0)) in the concentration of the predetermined substance thatis calculated by the time-lapse-change-calculating unit 15.Specifically, the correcting unit 16 is capable of obtaining a clearanceCL(t) corrected in accordance with Expression (g) below.

CL(t)=(Abs(t)/(Abseq(0)×(Cb(t)/Cb(0)))×Qd(t)  Expression (g)

As described above, the clearance (CL) calculated by theclearance-calculating unit 13 is corrected in accordance with thetime-lapse change in the concentration of the predetermined substance(Cb(t)/Cb(0)) calculated by the time-lapse-change-calculating unit 15.Therefore, even if the concentration (Cb) of the predetermined substancein the blood flowing through the blood circuit 1 changes with theprogress of the blood purification treatment, the clearance (CL) can becorrected correspondingly, with an estimation of the concentration to beobserved after such a change. Hence, even if the concentration (Cb) ofthe predetermined substance in the blood flowing through the bloodcircuit 1 changes moment by moment with the progress of the bloodpurification treatment, clearance (CL) can be obtained accuratelywithout repeatedly performing the establishment of a state ofequilibrium and the storing of an equilibrium value.

Furthermore, in the present embodiment, the clearance (CL) calculated bythe clearance-calculating unit 13 can be used for calculating dialysisdose Kt, which is a dialysis dose not standardized by V denoting thetotal body-fluid volume used in an index Kt/V representing thestandardized dose of dialysis performed by the dialyzer 2. That is,“Kt(te)” not standardized by V (total body-fluid volume) is calculableby integrating CL(t) obtained over time, as defined by Expression (h)below. Note that “te” denotes the end time of the blood purificationtreatment.

[Math. 1]

Kt _((te))=∫₀ ^(te) CL(t)dt  Expression (h)

As described above, Kt (i.e., Kt(te) in Expression (h) above) notstandardized by V denoting the total body-fluid volume used in the indexKt/V representing the standardized dose of dialysis performed by thedialyzer 2 is calculated in accordance with the clearance (CL)calculated by the clearance-calculating unit 13. Therefore, for example,if the index Kt (Kt(te)) not standardized by V is displayed by thedisplay unit 14 in correspondence with the intention of medical workersincluding doctors, the medical workers can grasp the index Kt (Kt(te)).

In addition, in the present embodiment, the number of times of reuse ofthe dialyzer 2 is quantitatively evaluatable in accordance with theclearance (CL) calculated by the clearance-calculating unit 13.Specifically, if the treatment is repeatedly given to one specificpatient with one specific dialyzer 2, for example, clearance (CL) iscalculated by the clearance-calculating unit 13 at the beginning or theend of the treatment and is displayed on the display unit 14 or storedin the storage unit 12. Hence, the tolerable number of times of reuse ofthat specific dialyzer 2 can be evaluated objectively and appropriately.

Now, a process of calculating clearance that is undergone by the bloodpurification apparatus according to the present embodiment will bedescribed with reference to the flow chart illustrated in FIG. 3.

First, the blood pump 3 and the duplex pump P are activated with thearterial puncture needle (a) and the venous puncture needle (b) beingpunctured in the patient, whereby blood is caused to flow into the bloodcircuit 1 through the dialyzer 2 while dialysate is caused to flowthrough the dialysate introduction line 7 and the dialysate drain line8. In the above state, in step S1, the dialysate flow rate (Qd) isreduced by a predetermined value. Then, in step S2, the process isstopped until the value (the concentration Cd of the predeterminedsubstance or the absorbance (Abs)) detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)is stabilized. When the value is judged to be stabilized, the processproceeds to step S3, where the relationship between the dialysate flowrate (Qd) and the detected value (the concentration Cd of thepredetermined substance or the absorbance (Abs)) is stored in thestorage unit 12.

Then, in step S4, whether there is any change greater than or equal to apredetermined threshold in the value detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)is checked. If there is a change greater than or equal to thepredetermined threshold, the process returns to step S1, where thedialysate flow rate (Qd) is reduced by a predetermined value.Furthermore, steps S2 to S4 are performed sequentially. If it is judgedin step S4 that there is no change greater than or equal to thepredetermined threshold in the value detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)(i.e., if the detected value is judged to be constant), the processproceeds to step S5, where the detected value is stored as anequilibrium value (an equilibrium concentration (Cdeq) or an equilibriumabsorbance (Abseq)) in the storage unit 12.

Specifically, as illustrated in FIG. 4, when the dialysate flow rate(Qd) is sequentially reduced from point (A) to point (D) and is furtherreduced from point (D), the value (the concentration (Cd) of thepredetermined substance or the absorbance (Abs)) detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)becomes constant, establishing a “state of equilibrium”. Therefore, thevalue detected in the state of equilibrium (at point D) is stored as anequilibrium value (an equilibrium concentration (Cdeq) or an equilibriumabsorbance (Abseq).

Then, the process proceeds to step S6, where the clearance-calculatingunit 13 calculates clearance (CL) through a mathematical expressionCL=(Cd/Cdeq)×Qd (where CL denotes clearance, Cd denotes theconcentration of the predetermined substance detected by theconcentration-detecting unit, Cdeq denotes the equilibrium value storedin the storage unit, and Qd denotes dialysate flow rate), or amathematical expression CL=(Abs/Abseq)×Qd (where CL denotes clearance,Abs denotes the absorbance detected by the detecting portion, Abseqdenotes the equilibrium value stored in the storage unit, and Qd denotesdialysate flow rate).

When the clearance (CL) is obtained in step S6, as illustrated in FIG.4, the storage unit 12 can store not only the equilibrium value (Cdeq orAbseq) and the relationship between the dialysate flow rate (Qd) and thevalue (Cd or Abs) detected by the waste-liquid-concentration sensor 5(the concentration-detecting unit) (see the upper graph in the drawing)but also the relationship between the dialysate flow rate (Qd) and theclearance (CL) (see the lower graph in the drawing).

According to the present embodiment, a state of equilibrium isestablished by reducing the dialysate flow rate (Qd). Alternatively, astate of equilibrium may be established by increasing the blood flowrate (Qb). In the latter case, in step S1, the blood flow rate (Qb) isincreased by a predetermined value. Subsequently, in step S2, theprocess is stopped until the value (the concentration Cd of thepredetermined substance or the absorbance (Abs)) detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)is stabilized. Then, when the value is judged to be stabilized, theprocess proceeds to step S3, where the relationship between the bloodflow rate (Qb) and the detected value (the concentration Cd of thepredetermined substance or the absorbance (Abs)) is stored in thestorage unit 12.

Specifically, as illustrated in FIG. 5, when the blood flow rate (Qb) issequentially increased from point (A) to point (D) and is furtherincreased from point (D), the value (the concentration (Cd) of thepredetermined substance or the absorbance (Abs)) detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)becomes constant, establishing a “state of equilibrium”. Therefore, thevalue detected in the state of equilibrium (at point (D)) is stored asan equilibrium value (an equilibrium concentration (Cdeq) or anequilibrium absorbance (Abseq).

The control unit 11 according to the present embodiment establishes a“state of equilibrium” by reducing the dialysate flow rate (Qd) orincreasing the blood flow rate (Qb) as described above. Alternatively, astate of equilibrium may be established by setting the dialysate flowrate (Qd) to 0 (stop supplying the dialysate) or causing the dialysateto circulate through the dialyzer 2 (the blood purifier). As describedabove, the control unit 11 establishes a state of equilibrium byreducing or stopping the dialysate flow rate (Qd), increasing the bloodflow rate (Qb), or causing the dialysate to circulate through thedialyzer 2. Thus, a state of equilibrium can be established simply andeasily.

According to the above embodiment, a state of equilibrium is establishedwhere the concentration of the predetermined substance in the wastedialysate flowing through the dialysate drain line 8 and theconcentration of the predetermined substance in the blood flowingthrough the blood circuit 1 (at the inlet of the dialyzer 2) are equalor approximate to each other. Furthermore, the value detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)in the state of equilibrium is stored as an equilibrium value.Furthermore, clearance (CL) is calculated in accordance with the value(Cd, Abs) detected by the waste-liquid-concentration sensor 5 and theequilibrium value (Cdeq, Abseq) stored in the storage unit 12.Therefore, clearance can be obtained in real time.

Furthermore, the clearance-calculating unit 13 according to the presentembodiment calculates clearance through a mathematical expressionCL=(Cd/Cdeq)×Qd (where CL denotes clearance, Cd denotes theconcentration of the predetermined substance detected by theconcentration-detecting unit, Cdeq denotes the equilibrium value storedin the storage unit, and Qd denotes dialysate flow rate). Therefore,clearance can be calculated correctly and easily with thewaste-liquid-concentration sensor 5 (the concentration-detecting unit),which detects the concentration of the predetermined substance in thewaste dialysate.

Furthermore, the waste-liquid-concentration sensor 5 (theconcentration-detecting unit) according to the present embodimentincludes the light-emitting portion 17 that emits light toward the wastedialysate, the light-receiving portion 18 capable of receiving the lightemitted from the light-emitting portion 17 and transmitted through thewaste dialysate, and the detecting portion 19 that detects theabsorbance in accordance with the intensity of the light received by thelight-receiving portion 18. Furthermore, the waste-liquid-concentrationsensor 5 detects the concentration of the predetermined substance in thewaste dialysate in accordance with the absorbance detected by thedetecting portion 19. Therefore, the concentration of the predeterminedsubstance in the waste dialysate can be detected accurately withoutbringing the waste dialysate into contact with any sensor or the like.

According to the present embodiment, the storage unit 12 is capable ofstoring the absorbance detected by the detecting portion 19 in the stateof equilibrium as an equilibrium value (Abseq). Furthermore, theclearance-calculating unit 13 calculates clearance in accordance withthe absorbance (Abs) detected by the detecting portion 19 and theequilibrium value (Abseq) stored in the storage unit 12. Therefore,clearance can be obtained in real time by utilizing the ratio of theabsorbance that correlates with the ratio of the concentration of thepredetermined substance.

In particular, the clearance-calculating unit 13 according to thepresent embodiment calculates clearance through a mathematicalexpression CL=(Abs/Abseq)×Qd (where CL denotes clearance, Abs denotesthe absorbance detected by the detecting portion, Abseq denotes theequilibrium value stored in the storage unit, and Qd denotes dialysateflow rate). Therefore, clearance can be calculated correctly and easilyby utilizing the ratio of the absorbance that correlates with the ratioof the concentration of the predetermined substance.

Furthermore, the blood purification apparatus includes thetime-lapse-change-calculating unit 15 that calculates the time-lapsechange in the concentration of the predetermined substance in the bloodflowing through the blood circuit 1 in accordance with the clearancecalculated by the clearance-calculating unit 13. Therefore, theconcentration of the predetermined substance in the blood flowingthrough the blood circuit at the current time or at any point of timethereafter can be estimated.

Furthermore, the blood purification apparatus includes the correctingunit 16 that corrects the clearance calculated by theclearance-calculating unit 13, in accordance with the time-lapse changein the concentration of the predetermined substance that is calculatedby the time-lapse-change-calculating unit 15. Therefore, even if theconcentration of the predetermined substance in the blood flowingthrough the blood circuit 1 changes with the progress of the bloodpurification treatment, the clearance can be corrected correspondingly,with an estimation of the concentration to be observed after such achange.

Furthermore, dialysis dose Kt as an index not standardized by V denotingthe total body-fluid volume used in the index Kt/V representing thestandardized dose of dialysis performed by the dialyzer 2 is calculatedin accordance with the clearance calculated by the clearance-calculatingunit 13. Therefore, medical workers including doctors can grasp theindex Kt, which is not standardized by V, in correspondence with theirintention. Specifically, the standardized dialysis dose (Kt/V) is anindex obtained by substituting the difference in the concentration ofurea nitrogen in the waste dialysate between that at the beginning ofthe hemodialysis treatment and that at the current time, the volume ofultrafiltration during the hemodialysis treatment (blood purificationtreatment), and the time in the hemodialysis treatment into apredetermined mathematical expression:−In(C(e)/C(s)−0.0080+(4−3.5×C(e)/C(s))×(V_(UF)/DW) (where C(s) denotesthe urea-nitrogen concentration (initial value) at the beginning of thehemodialysis treatment, C(e) denotes the urea-nitrogen concentration atthe end of the dialysis, V_(UF) denotes ultrafiltration volume, and DWdenotes the patient's dry weight). Therefore, it has been difficult toobtain only the index Kt that is not standardized by V. In contrast,according to the present embodiment, only the index Kt that is notstandardized by V can be obtained through Expression (h) given above, inwhich clearance is used as a parameter. Therefore, the index Kt that isnot standardized by V can be obtained easily.

In addition, according to the present embodiment, the tolerable numberof times of reuse of the dialyzer 2 is quantitatively evaluated inaccordance with the clearance calculated by the clearance-calculatingunit 13. Therefore, if the treatment is repeatedly given to one specificpatient with one specific dialyzer 2, the tolerable number of times ofreuse of that specific dialyzer 2 can be evaluated objectively andappropriately.

While the present embodiment has been described above, the presentinvention is not limited thereto. For example, the value detected by thewaste-liquid-concentration sensor 5 (the concentration-detecting unit)and the equilibrium value that are to be used for calculating theclearance may be replaced with other parameters, as long as suchparameters each correlate with the concentration of the predeterminedsubstance. For example, factors such as the voltage or the currentoutputted by the waste-liquid-concentration sensor 5 may be employed inaddition to the absorbance. Moreover, the mathematical expressions forcalculating clearance by the clearance-calculating unit 13 are notlimited to those given above, and may be other mathematical expressions.

While the present embodiment concerns a case where the calculatedclearance is displayed on the display unit 14, the calculated clearancemay be informed to medical workers including doctors through anotherunit such as a speaker. Alternatively, instead of providing ordisplaying such information, the clearance calculated by theclearance-calculating unit 13 may be, for example, exclusively used forinternal processing performed for making settings of the treatment.While the present embodiment is applied to a hemodialysis apparatus, thepresent invention may also be applied to a blood purification apparatusintended for another treatment (such as hemofiltration treatment orhemodiafiltration treatment) for purifying blood while causing the bloodto extracorporeally circulate.

The present invention is applicable to any blood purification apparatus,including those having other additional functions, as long as theapparatus includes a control unit that establishes a state ofequilibrium where the concentration of a predetermined substance inwaste dialysate flowing through a dialysate drain line and theconcentration of the predetermined substance in blood flowing through ablood circuit are equal or approximate to each other, a storage unitcapable of storing a value detected by a concentration-detecting unit inthe state of equilibrium as an equilibrium value, and aclearance-calculating unit capable of calculating clearance inaccordance with the value detected by the concentration-detecting unitand the equilibrium value stored in the storage unit, the clearancebeing a figure of merit representing the degree of solute removal by ablood purifier.

REFERENCE SIGN LIST

-   -   1 blood circuit    -   1 a arterial blood circuit    -   1 b venous blood circuit    -   2 dialyzer (blood purifier)    -   3 blood pump    -   4 a, 4 b air-trap chamber    -   5 waste-liquid-concentration sensor (concentration-detecting        unit)    -   6 dialysis device    -   7 dialysate introduction line    -   8 dialysate drain line    -   9 bypass line    -   10 ultrafiltration pump    -   11 control unit    -   12 storage unit    -   13 clearance-calculating unit    -   14 display unit    -   15 time-lapse-change-calculating unit    -   16 correcting unit    -   17 light-emitting portion    -   18 light-receiving portion    -   19 detecting portion    -   P duplex pump

1. A blood purification apparatus to which a blood circuit that allows apatient's blood to extracorporeally circulate and a blood purifierconnected to the blood circuit and that purifies the blood inextracorporeal circulation are attachable, the blood purificationapparatus including: a dialysate introduction line through whichdialysate is introduced into the blood purifier; a dialysate drain linethrough which waste dialysate resulting from blood purificationperformed by the blood purifier is drained from the blood purifier; anda concentration-detecting unit that detects a concentration of apredetermined substance in the waste dialysate resulting from the bloodpurification by the blood purifier and flowing through the dialysatedrain line, the blood purification apparatus comprising: a control unitthat establishes a state of equilibrium where the concentration of thepredetermined substance in the waste dialysate flowing through thedialysate drain line and a concentration of the predetermined substancein the blood flowing through the blood circuit are equal or approximateto each other; a storage unit storing a value detected by theconcentration-detecting unit in the state of equilibrium as anequilibrium value; and a clearance-calculating unit that calculatesclearance in accordance with the value detected by theconcentration-detecting unit and the equilibrium value stored in thestorage unit, the clearance being a figure of merit representing adegree of solute removal by the blood purifier.
 2. The bloodpurification apparatus according to claim 1, wherein theclearance-calculating unit calculates clearance through a mathematicalexpression CL=(Cd/Cdeq)×Qd (where CL denotes clearance, Cd denotes theconcentration of the predetermined substance detected by theconcentration-detecting unit, Cdeq denotes the equilibrium value storedin the storage unit, and Qd denotes dialysate flow rate).
 3. The bloodpurification apparatus according to claim 1, wherein the control unitestablishes the state of equilibrium by reducing or stopping thedialysate flow rate, increasing the blood flow rate, or causing thedialysate to circulate through the blood purifier.
 4. The bloodpurification apparatus according to claim 1, wherein theconcentration-detecting unit includes a light-emitting portion thatemits light toward the waste dialysate, a light-receiving portion thatreceives the light emitted from the light-emitting portion andtransmitted through the waste dialysate, and a detecting portion thatdetects absorbance in accordance with an intensity of the light receivedby the light-receiving portion, the concentration-detecting unitdetecting the concentration of the predetermined substance in the wastedialysate in accordance with the absorbance detected by the detectingportion.
 5. The blood purification apparatus according to claim 4,wherein the storage unit stores, as the equilibrium value, theabsorbance detected by the detecting portion in the state ofequilibrium, and the clearance-calculating unit calculates clearance inaccordance with the absorbance detected by the detecting portion and theequilibrium value stored in the storage unit.
 6. The blood purificationapparatus according to claim 5, wherein the clearance-calculating unitcalculates clearance through a mathematical expression CL=(Abs/Abseq)×Qd(where CL denotes clearance, Abs denotes the absorbance detected by thedetecting portion, Abseq denotes the equilibrium value stored in thestorage unit, and Qd denotes dialysate flow rate).
 7. The bloodpurification apparatus according to claim 1, further comprising atime-lapse-change-calculating unit that calculates a time-lapse changein the concentration of the predetermined substance in the blood flowingthrough the blood circuit, in accordance with the clearance calculatedby the clearance-calculating unit.
 8. The blood purification apparatusaccording to claim 7, further comprising a correcting unit that correctsthe clearance calculated by the clearance-calculating unit, inaccordance with the time-lapse change in the concentration of thepredetermined substance that is calculated by thetime-lapse-change-calculating unit.
 9. The blood purification apparatusaccording to claim 1, wherein dialysis dose Kt is obtained in accordancewith the clearance calculated by the clearance-calculating unit, thedialysis dose Kt being an index not standardized by V denoting a totalbody-fluid volume used in an index Kt/V representing a standardized doseof dialysis performed by the blood purifier.
 10. The blood purificationapparatus according to claim 1, wherein a tolerable number of times ofreuse of the blood purifier is quantitatively evaluated in accordancewith the clearance calculated by the clearance-calculating unit.
 11. Theblood purification apparatus according to claim 1, wherein the bloodcircuit and the blood purifier are attached.